DEXA discrete op-amps in the house.....err I mean the EE Mini Max Dac Plus

heiney9

Around Christmas time Parts Connexion had a 20% off all items sale. Me being me, I am always looking for a good deal. I had been reading about DEXA and Burson discrete op-amps. Integrated Circuit op-amps are usually a weak link and short cut many manufacturers employ to save money in designs. Rarely is an I/C op-amp designed for optimum audio performance. They are usually generic workhorses designed to work in many different types of applications.

http://www.enjoythemusic.com/magazine/equipment/1212/eastern_electric_minimax_dac_plus.htm

http://www.dagogo.com/audio-blast-eastern-electric-minimax-dac-plus-discrete-opamp-rolling

So far about 10 hours on a pair of DEXA dual op-amps for the tube output section and they are superb. Very organic and natural sounding. The EE Mini Max Plus Dac uses 2 single channel and 2 dual channel op-amps. They are socketed so it easy to make the swap. Like rolling tubes. The cost is not cheap, but the payoff is huge.

More to come as these break in. If I decide to use the solid state output I'll need to replace the 2 single channel op-amps, but so far I'm just using the tube output.

http://www.partsconnexion.com/opamp_dexa.html

H9

I will probably buy a pair for my Keces dac in the office rig since they are socketed too.

heiney9

I used a pair of dual OPA-627's in the Adcom GDA600 when I modded it. For an I/C op-amp that is one of the more expensive pieces and also one of the best sounding for that type of op-amp. But the discrete DEXA takes it up another couple levels, even before they are broken in.

strider

Very cool. Keep us updated as you get some more time on them.

Have you seen the Audio GD discrete op-amps? A bit cheaper, I remember reading positive reviews when I was researching them. That project fizzled out, so I never placed an order. Here's a link if interested: http://www.audio-gd.com/Pro/diy/OPA/OPAEN.htm

heiney9

I remember those being popular a few years ago. I don't know how they can sell them that cheaply, plus I don't like the fact that they need to be connected to ground to run at the optimum.

I will re-read the reviews because I want to replace the I/C op-amps in my Keces DA-151 with discrete op-amps. Since it's a secondary (office rig) I'd like to keep the cost down. I can get (2) OPA-Moon's for the cost of a single Dexa.

Decisions....decisions.....

There is another vendor getting really, really good reviews too, but they aren't any less expensive than the Burson or Dexa. I didn't choose Sparkos because of the increased gain they output. I have more than enough gain and even more would not have been ideal.

Lot's of reviews out there for this company.

http://sparkoslabs.com/

Anyone serious about their rig which uses op-amps should consider discrete op-amps. The Dexa's aren't even broken in yet and the increased clarity, image sharpness and ambient detail retrieval while sounding more organic and analog are remarkable over the $2 all purpose op-amp.

A full review to come after about 150 hours of break in. It can only get better.

H9

heiney9

A bit of an update.

FANTASTIC! Clarity, separation, detail, air, effortless..............as they continue to break in those are the words that come to mind.

There is a clarity to the music (good or bad depending on the recording) that just keeps on popping up. Standard op-amps are pretty good but they just don't have the ability to really sharpen things up and resolve like this. Ambient details are very present which tend to be missing using the regular op-amps.

I just listened to many tracks from Led Zeppelin - How the West Was Won. By today's standards not an "audiophile" recording. But a remastered live recording from the 70's. What struck me listening tonight is I felt like I was right on stage with the band. This recording was a multi track mix from the soundboard so the audience is way in the background. Before I always felt like I was in about the 6th row. Tonight, it was amazing the shift of perspective because of the clarity, ambient details and naturalness of presentation.

The bass was crushing as well, both Bonhma's attacks of the kick drum and Jonsey's bass notes on Dazed and Confused, thought I was going to break a window.

Again, this wouldn't qualify even close to being an audiophile recording.

Discrete is the only way to go. I will be replacing the op-amps in my Keces DA-151 as well in the office rig.

It can only get better as these aren't even broken in yet.

H9

heiney9

One other thing is, I find myself listening at louder levels because it's seems much more analog and much of the digital nasties have been eliminated.

heiney9

Guys. seriously if you have a higher end piece that uses op-amps in the signal chain. You NEED to get some discrete units. I/C op-amps are very generic and will never give you the ultimate in sound reproduction. (If that is your goal)

The difference is so positive and apparent.

Next up, for peace of mind I am going to tackle swapping out the I/C based voltage regulators w/Dexa discrete regulators. There are 2 for the solid state output and 1 for the tube output. 7813 runs the tube filament circuit and 7815 & 7915 supply the op-amps.

http://www.partsconnexion.com/prod_pdf/dexa.pdf

heiney9

I will need to get my learn on however. I know the "78" in 7813 means positive and "79" means negative. I am assuming the next number is the voltage, ie; 7813 is positive 13v, 7815 is positive 15v and 7915 is negative 15v.

Problem 1 is the Dexa regulators only comes in 7812/7912 or 7815/7915. So for the tube filament circuit do I go with the 7812 or 7815 in place of the 7813?

All this before I have even googled anything.

H9

P.s. There are extensive threads on op=amp rolling for this unit. But, no one seems to have upgraded any other parts except the tube output coupling caps. Wayne from Boulder has done an extensive mod, but it's proprietary.

agfrost

Interested in your take on (potentially) using these in your DACs, Brock, as you and I both have a Keces and a modded Adcom 600.

Reading your impressions and your enthusiasm here is piquing my own curiosity...

Jay

heiney9

Jay, the Dexa discrete op-amps are superb. They were plug in play for the EE Dac Plus. (I checked with the designer as well as all the people currently running them). With the older Adcom, you might want to make sure there is enough current supplied to run the new ones, they draw quite a bit more than the standard I/C opamp.

Since the one's I replaced were dual (channel) I could theoretically swap them in the Adcom, but w/o knowing for sure they would function properly, I won't. Too expensive to "release the smoke"

I know of some people using the single (channel) version in their Keces dac's. The Keces has a pretty robust ps section so I think it would be ok.

As far as the discrete regulators, I did buy the Burson models a few years ago (geez, like 5-6 years) and never installed them in the Adcom, still have them in my parts box.

I am told the super regulators from Dexa are drop in's for the 78xx and 79xx models used in most digital circuits. What I don't know is the added benefit. @$35/ea it gets expensive quickly and so far I don't see a whole lot of DIYer reports on these. Discrete has always been better than an I/C, but to what degree in this case.

Hard core DIYer's (like Rich) build their own shunt regulators (which are superior). Those are not for the faint at heart and they are much, much larger and bulkier and more expensive. These are plug in play and even attach to the same heat sink.

I will probably get the (3) mentioned and swap them and see if there is an improvement. I am a BIG believer in everything matters, and the cumulative benefits of many small improvements.

Discrete op-amps, discrete regulators and better coupling caps. Should be a win/win/win. Total parts cost in the neighborhood of $300 for the tube section. I chose not to replace the op-amps running the solid state section at this time, since I am only using the tube output of the dac. The SS are single (channel) and could be shared with the Keces as it takes singles as well.

The only thing it can hurt is my wallet......lol

H9

P.s. the EE Mini Max Dac Plus is no slouch stock, these tweaks are just some fine tuning that results in more clarity, air and analog sounding output.

agfrost

Thanks for your thoughts, Brock.

heiney9

No problem Jay.

For the time being I am going to let the Dexa discrete op-amps break in and listen and enjoy for awhile. Then onto the voltage regs and coupling caps upgrade. I like tinkering (soldering) outside since natural sunlight is better than lamps in the basement for soldering. So maybe in the next month or so I'll start the next step.

H9

lightman1

Nelson Pass is a hack...
How bout it B!!!!

ken brydson

lightman1 wrote: »

Nelson Pass is a hack...
How bout it B!!!!

Pass it to the right man...Hey, it's legal here in Warshington

txcoastal1

lightman1 wrote: »

Nelson Pass is a hack...
How bout it B!!!!

You forgot about overrated too

heiney9

Really guys? Are you that bored you have to muck up my DIY thread?

lightman1

Bustin yer chops, B. You have provided a wealth of info here. I've got a couple of the Emerald Physics amps. I'll study up on them and see if there is a way to utilize these in the circuit. It may put a little life into them.

heiney9

I am not familiar with the EP amps. It's possible they use op-amps at the output depending on the design. If they do, discrete can really make a positive difference.

Rock on with your pants on...

H9

EndersShadow

heiney9 wrote: »

Rock on with your pants on...

You know thats not how he rolls...

lightman1

They're class D amps. Kinda sterile sounding.

heiney9

The rabbit hole never ends.... DEXA has introduced a new single and dual Ultimate Edition discrete op-amp that is better than the Limited Edition units I bought just a few years ago.

http://www.newclassd.com/index.php?page=124&hv=1



http://www.newclassd.com/index.php?page=125&hv=1



I am now tempted to try these. If I do, I'll probably sell the current DEXA's.

H9